— 129 — 
my description, above, I agree principally with Leydig, as to the 
nature of the two substances, but we do not agree as to their 
structure. Leydig calls the substance of his reticulation spongio- 
plasm; as I have tried to distinguish between spongioplasm and neii- 
roglia, I have called the same substance neiiroglia, which, however, 
in my opinion, forms tubes (enveloping primitive tubes or nerve-tubes) 
and not a sponge-work in the dotted substance. Leydig does not 
draw any line of demarcation between spongioplasm and neuroglia. 
His opinion is that, what he calls spongioplasm is a reticulated sub- 
stance which is present in the ganglion cells, as well as in the cells 
of the neuroglia, or the connective-tissue as he calls it; and that 
there is, in the nerve-system of the vertebrates, an intimate connec- 
tion between the spongioplasm of both kinds of cells (cf op. cit. 
p. 187 — 189). In a future paper on the structure of the neu- 
roglia, the writer will have an opportunity to treat of this subject 
more circumstantially. 
The origin of the primitive tubes and fihrillæ of the 
dotted substance. — Having described what the constituents of 
the dotted substance are, as far as our ability goes, we will now 
advance to examine from whence these constituents come. To do this, 
we must try to learn the course of the nervous processes, issuing 
from the ganglion cells, and the nerve-tubes in the dotted substance. 
We have, already, said that the nervous processes of the ganglion 
cells occasionally subdivide, and give off branches, on their course 
from the ganglion cells to the dotted substance. On a closer 
examination we will find that they do the same, in a higher degree, 
on their course through the dotted substance. 
Uti This subdivision and branching of the nervous processes cannot 
easily be traced, without staining by the chromo-silver method 
(cf p. 78). In successful preparations, stained in this way, I have 
occasionally been able to trace the nervous processes, to some ex- 
tent, on their course through the dotted substance. When a nervous 
process was visible for some distance along its course dichotomous 
subdivisions, or finer side-branches given off from it, were always 
observed; I have never observed a nervous process which, for any 
considerable length, had an isolated course through the dotted sub- 
stance. 
On comparison of the course of the various nervous processes, 
I have found that they essentially differ, and that there must be two 
kinds or types of them, which behave in two different ways on 
their course through the dotted substance. 
9 
